Created attachment 262878 [details] [Animated GIF] Bug Works as expected on El Capitan's Safari 9.0, broken in WebKit Nightly. Most likely a WebKit regression in flexbox. There weren't any HTML or CSS changes in the Inspector related to this bug. I'm working on isolating the issue.
<rdar://problem/23066349>
Take a look at https://bugs.webkit.org/show_bug.cgi?id=149725. I fixed a regression caused by http://trac.webkit.org/changeset/189567, which changed the min-width/height defaults to auto for flex box items. Sounds similar.
Created attachment 262975 [details] Patch (In reply to comment #2) > Take a look at https://bugs.webkit.org/show_bug.cgi?id=149725. I fixed a > regression caused by http://trac.webkit.org/changeset/189567, which changed > the min-width/height defaults to auto for flex box items. Sounds similar. Thanks, that was it!
Comment on attachment 262975 [details] Patch r=me
Comment on attachment 262975 [details] Patch Clearing flags on attachment: 262975 Committed r191004: <http://trac.webkit.org/changeset/191004>
All reviewed patches have been landed. Closing bug.